Fluid cooling plant for mines



Filed Co t. 15, 1952 FLUID COOLING PLANT FOR MINES 2 Sheets-Sheet l lnvenfor MMMv 4;, Aft-omen Oct. 23, 1956 J. c. GREY 2,767,560

v FLUID COOLING PLANT FOR MINES Filed Oct. 13,- 1952 2 Sheets-Sheet 2 COOLING WATER 2 3 T ,4 T J, A/R m OR 007' J l I i /7 i F'L Y l fmo v Inventor 4;, Alf-omen- United States Patent ce 2,767,550 COOLING P NT F R John Constantine Grey, Isleworth, England, assignor to Power Jets (Research & Development) Limited, "Lon- Claims priority, application Great Britain October ;29, 195 1 1 Claim. or. 2 134 This invention relates to mine airconditionin-g arrangements.

It is known to use refrigerating plant for the provision of cool mine air and in the Union of South Africa where there are very deep gold mines in which the mine air is naturally hot and damp such refrigerating plant is frequently established at the surface of the mine. The cold air produced is taken by pipe to the bottom of the mine and circulation of the air within the mine is insured by large axial fans accommodated at the surface end of upcast shafts. Rock face temperatures reach value such as 49 centigrade (120 Fahrenheit) so that there is a steady temperature rise in the cool air coming down the shaft. In order to maintain an acceptable temperature at the working face the air has to be cooled at the surface much below the temperature required at the face. The result is the refrigerating plant is much larger than is really necessary and a break-down of the main unit affects the entire mine.

A proposal has also been made to design the refrigerating plant so that it can be situated within the mine. Air coolers were to be separately positioned around the mine and each air cooler was to be linked to the central plant so as to transfer heat from the hot mine air adjacent to the cooler to the refrigerant in the refrigerating plant. A cold vapour process was proposed for the refrigerating plant and a water or brine circulating system connected the plant to the coolers in parallel. The refrigerating plan-t comprised a rotary compressor which was to be driven by an air turbine supplied with compressed ,air from the surface of the mine. Each of the air coolers also comprised an air turbine driven in like manner and drivin g a fan.

In any mine air conditioning arrangement that is to be acceptable and which is to be adopted in practice it is essential that the equipment should be simple and that the arrangement as a whole should be as flexible as possible.

The present invention provides a mine air conditioning arrangement comprising a refrigerating plant designed to be situated within the mine and a number of air coolers suitable for separate positioning about the mine each cooler being arranged to be linked to said plant so as to transfer heat from the hot mine air to the refrigerant, characterised by said plant comprising a closed cycle gaseous refrigerant unit embodying rotary compression and expansion machines which are arranged to be locally driven.

The compression and expansion machines may be mounted on the same shaft so that work of expansion in the cycle may reduce the external work required for operating the unit. The machines may be respectively centrifugal and centripetal so that the refrigerant unit may occupy a minimum of space. Builtinto the unit as an integrally assembled structure there may be the heat input and heat rejection stage heat exchangers of the refrigerating cycle. Such a construction reduces duct 2 ,767,560 en 9st.- ZS, 195.16

2 losses and enables considerable space saving to be achieved.

The mine coolers may each incorporate a locally driven fan and be connected by one set only of fluid connections to the refrigerating unit. Through those fluid connections there maybe circulated a liquid of low freezing point such as brine or water.

The refrigerant employed in the gaseous refrigerant uni-t is preferably dry air. It may be convenient to extract from the refrigerating cycle at some point a supply of cold air provided that its return to the closed cycle is also accounted for.

The present invention also provides a method of conditioning mine air in which hot damp air is blown by a fan through a liquid/ air cooler wherein heat is transferred from the air to the liquid, in which said liquid is circulated through flexible lagged piping between said cooler and a heat exchanger situated also at the bottom of the mine, the heat exchanger transferring heat from said liquid to a gas, in which said gas forms the refrigerant .in an adjacent closed cycle refrigerating unit in which the compression and expansion stage in the refrigerating cycle are accomplished by gas flow through rotary machines and in which heat is transferred from the refrigerg water supply between said compression and expansion stages.

The invention will be described with reference to one embodiment thereof shown in the accompanying drawings in which:

Figure '1 ,shows diagrammatically fluid cooling plant situated at the bottom of a mine shaft for conditioning mineair.

Figure 2 shows in some more detail one kind of me.- chanical construction which may be employed for the equipment indicated in Figure 1.

In Figure 1 there will be seen a compresor/turbine combination 1, 2 being driven by an electric motor 3. The compressor and turbine form part of a closed cycle gaseous refrigerating equipment using dry air as the refrigerant. The air is expanded in the turbine 2 to a low temperature, e. g. about l0 C., vafter which is passes through a 'heat exchanger 4 in which heat is transferred to it from water passing through the other half of the exchanger. The dry air is compressed in the compressor 1 after which it passes through another heat exchanger 5 in which it is cooled, heat being transferred to water passing through the other half of this exchanger. The cooled air is now returned to the turbine for re-expansion, thereby completing the closed refrigerating cycle. The water supply for the heat exchanger ,5 is shown provided in a closed circuit incorporating a cooling tower 6 and a pump 7 The cooling tower is indicated as being situated near the bottom of a mine upcast shaft 8. Alternai e y t e w e supply fo t h a xch n e 5 ay be provided from a supply at the surface via the pipe 9, later being pumped back up the shaft via the pipe 10.

The water supply for the heat exchanger 4 is circulated in a closed system by a pump 11. As it passes through the heat exchanger 4 it is cooled. Following this it is used in a water/air cooler 12 to cool a supply of urine air delivered by a fan 13 through the cooler. After flowing through the cooler the water, which is now warm, is returned to the heat exchanger 4 where it is again cooled. The outlet water temperature from this exchanger may be arranged to be of the order 3 to 5 C.

By the plant arrangement shown in Figure 1 warm mine air, being saturated and at a temperature of 32 C., delivered by a fan to the cooler is arranged to emerge from the cooler at a temperature of 27 C. In order to achieve this improvement the power consumption of the motor 3, the pumps and the fan and the working pressure ratio of the refrigerating cycle are determined primarily by the temperature of the cooling water available to the.

heat exchanger ures given below it is assumed that with the cooling tower. arrangement water can be delivered to the heat exchanger at a temperature of 49 C. whilst from the surface it can be supplied at 27 C. If the expansion temperature of the dry air emerging from the expanding turbine 2 is taken as -5 C. and the air delivery through the cooler is taken as 30,000 cubic feet. per minute, the total power consumption would be either 210 H. P. or 142 H. P. according to whether the higher or lower temperature of cooling water was available for the heat exchanger 5. In the refrigerating cycle the pressure ratio will be either 2.5 or 1.8 in the light of the same circumstances. The ratio of the mass flow of dry airin the refrigerating cycle to the air delivery of the fan may be quoted as 0.17.

This plant will be able to be made in a conveniently simple manner and used for mine air conditioning in an effective and flexible way.

One form of construction of the plant is shown diagrammatically in Figure 2. The compressor/expander turbine 1, 2 may be made as a unit of two radial flow impellers back to back. There is a single drive shaft for these two rotary machines connected to the motor 3 via a gear box 14. Ducting leads the dry air from the compresser 1 to the heat exchanger 5 and back to the turbine 2. Similarly the air is fed from the radially-inward flow turbine to the compresser via the heat exchanger 4. These heat exchangers may be of the well known recuperative tube or secondary surface types. Cold water provided from the heat exchanger 4 is taken by lagged flexible hose 15 to the water/air cooler 12. This with its fan and circulating pump for the water may be constructed as a unit, drive for the fan and the pump being provided by an electric. motor 16. Warm returned to the heat exchanger 4 also by flexible hose. At 17 there is indicated an extension of the water circulating circuit across which may be connected a number of water/air coolers, all in parallel with the cooler 12. By these means the refrigerating cycleequipment may con veniently be placed at the bottom of the upcast shaft in which the cooling tower 6 is situated whilst coolers such as 12 may be situated Wherever they are required about the bottom of the mine.

The closed cycle refrigerating unit only handles a small proportion, 17% in the example quoted above, of the quantity of air actually conditioned. Because it is a closed cycle using a dry medium there is no possibility of trouble through dust or freezing. The number of coolers connected to the heat exchanger 4 via the water circulating hoses is determined, amongst other things, by the rate of heat transfer within the heat exchanger 4. This number may be varied at will be altering the level of gas pressures within the closed cycle providing, of course,

5. For the sake of the performance iig- Water from the cooler is.

. ing point either 2.5 or 1.8 makes ing a closed refrigerant circuit,

ated in said first duct, a second heat exchanger situated that the motor driving unit 3 is arranged to do the extra 5 work. The gas pressure level may be altered by means of the valve 18. Compressed dry air may be introduced into the cycle via this valve to increase prevailing pressure level or that load falls by blowing off frigeratiug unit. pressure of amount of level may be reduced if the air conditioning some of the air from the re- The motor torque needed and the mean the closed cycle fix a practical limit to the alteration to pressure level. that may be permitted but a fivefold "capacity increase may be com templated.

It will be apparent that with the closed air refrigerating cycle no question of humidity i involved and this again helps towards obtaining a saving of size and power apart from the elimination of any freezing troubles.

A further advantage obtained by the use of the closed cycle unit will be that of reduction in noise. possible to extract purposes, branches Moreover it may be cold air from the cycle for ancillary are then provided from the equipment of .plant according to the present invention.

Different values would be obtained with different examples and variations in plant layout are possible. fluid might be brine or any instead of water.

The circulating other liquid with a low freez- The pressure ratio quoted of possible the use of single stage impellers as the rotary machines in the refrigerating cycle.

What I claim is: Mine air conditioning arrangement incorporating a refrigerating plant designed for situation within the mine and comprising a centrifugal air compresser, a centripetal expander turbine drivingly connected to said centrifugal compressor, a first duct interconnecting the compresser outlet and the turbine inlet, a second duct interconnecting the turbine outlet and the compresser inlet thus completa first heat exchanger situin said second duct, a plurality of air coolers spaced about the mine, a closed fluid circuit through said coolers and a further closed fluid circuit through said tower and first heat exchanger providing a heat transfer path from said first heat exchanger to said fluid cooling tower.

References Cited in the file of this patent UNITED STATES PATENTS 

